Redmine

After upgrading to 1.0.1, on some issues I get this error:

@ActionView::TemplateError (undefined method `-' for nil:NilClass) on line #62 of app/views/issues/show.rhtml:
59:
60: <%= call_hook(:view_issues_show_description_bottom, :issue => @issue) >
61:
62: < if !@issue.leaf? || User.current.allowed_to?(:manage_subtasks, Herve Harster) %>
63: <hr />
64: <div id="issue_tree">
65: <div class="contextual">

app/views/issues/show.rhtml:62:in `_run_rhtml_app47views47issues47show46rhtml'
    app/controllers/issues_controller.rb.REMOTE.26955.rb:124
    app/controllers/issues_controller.rb.REMOTE.26955.rb:123:in `show'
    /usr/local/rvm/gems/ree-1.8.7-2010.01@redmine-0.9/gems/passenger-2.2.11/lib/phusion_passenger/rack/request_handler.rb:92:in `process_request'
    /usr/local/rvm/gems/ree-1.8.7-2010.01@redmine-0.9/gems/passenger-2.2.11/lib/phusion_passenger/abstract_request_handler.rb:207:in `main_loop'
    /usr/local/rvm/gems/ree-1.8.7-2010.01@redmine-0.9/gems/passenger-2.2.11/lib/phusion_passenger/railz/application_spawner.rb:418:in `start_request_handler'
    /usr/local/rvm/gems/ree-1.8.7-2010.01@redmine-0.9/gems/passenger-2.2.11/lib/phusion_passenger/railz/application_spawner.rb:358:in `handle_spawn_application'
    /usr/local/rvm/gems/ree-1.8.7-2010.01@redmine-0.9/gems/passenger-2.2.11/lib/phusion_passenger/utils.rb:184:in `safe_fork'
    /usr/local/rvm/gems/ree-1.8.7-2010.01@redmine-0.9/gems/passenger-2.2.11/lib/phusion_passenger/railz/application_spawner.rb:354:in `handle_spawn_application'
    /usr/local/rvm/gems/ree-1.8.7-2010.01@redmine-0.9/gems/passenger-2.2.11/lib/phusion_passenger/abstract_server.rb:352:in `__send__'
    /usr/local/rvm/gems/ree-1.8.7-2010.01@redmine-0.9/gems/passenger-2.2.11/lib/phusion_passenger/abstract_server.rb:352:in `main_loop'
    /usr/local/rvm/gems/ree-1.8.7-2010.01@redmine-0.9/gems/passenger-2.2.11/lib/phusion_passenger/abstract_server.rb:196:in `start_synchronously'
    /usr/local/rvm/gems/ree-1.8.7-2010.01@redmine-0.9/gems/passenger-2.2.11/lib/phusion_passenger/abstract_server.rb:163:in `start'
    /usr/local/rvm/gems/ree-1.8.7-2010.01@redmine-0.9/gems/passenger-2.2.11/lib/phusion_passenger/railz/application_spawner.rb:213:in `start'
    /usr/local/rvm/gems/ree-1.8.7-2010.01@redmine-0.9/gems/passenger-2.2.11/lib/phusion_passenger/spawn_manager.rb:262:in `spawn_rails_application'
    /usr/local/rvm/gems/ree-1.8.7-2010.01@redmine-0.9/gems/passenger-2.2.11/lib/phusion_passenger/abstract_server_collection.rb:126:in `lookup_or_add'
    /usr/local/rvm/gems/ree-1.8.7-2010.01@redmine-0.9/gems/passenger-2.2.11/lib/phusion_passenger/spawn_manager.rb:256:in `spawn_rails_application'
    /usr/local/rvm/gems/ree-1.8.7-2010.01@redmine-0.9/gems/passenger-2.2.11/lib/phusion_passenger/abstract_server_collection.rb:80:in `synchronize'
    /usr/local/rvm/gems/ree-1.8.7-2010.01@redmine-0.9/gems/passenger-2.2.11/lib/phusion_passenger/abstract_server_collection.rb:79:in `synchronize'
    /usr/local/rvm/gems/ree-1.8.7-2010.01@redmine-0.9/gems/passenger-2.2.11/lib/phusion_passenger/spawn_manager.rb:255:in `spawn_rails_application'
    /usr/local/rvm/gems/ree-1.8.7-2010.01@redmine-0.9/gems/passenger-2.2.11/lib/phusion_passenger/spawn_manager.rb:154:in `spawn_application'
    /usr/local/rvm/gems/ree-1.8.7-2010.01@redmine-0.9/gems/passenger-2.2.11/lib/phusion_passenger/spawn_manager.rb:287:in `handle_spawn_application'
    /usr/local/rvm/gems/ree-1.8.7-2010.01@redmine-0.9/gems/passenger-2.2.11/lib/phusion_passenger/abstract_server.rb:352:in `__send__'
    /usr/local/rvm/gems/ree-1.8.7-2010.01@redmine-0.9/gems/passenger-2.2.11/lib/phusion_passenger/abstract_server.rb:352:in `main_loop'
    /usr/local/rvm/gems/ree-1.8.7-2010.01@redmine-0.9/gems/passenger-2.2.11/lib/phusion_passenger/abstract_server.rb:196:in `start_synchronously'

Rendering /home/intweb/domains/rm-test.inteli-com.com/redmine/public/500.html (500 Internal Server Error)@

I'm not normally a RoR guy and I'm a bit lost. Any help?